In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and also more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing, using a polishing apparatus, while a polishing liquid containing abrasive particles such as silica (SiO2) or ceria (CeO2) therein is supplied onto a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing surface and is polished.
The polishing apparatus for performing the above CMP process includes a polishing table having a polishing pad serving as a polishing surface, and a polishing head for holding a substrate such as a semiconductor wafer. By using such a polishing apparatus, the substrate is held and pressed against the polishing pad under a predetermined pressure by the polishing head to polish an insulating film, a metal film or the like on the substrate.
As one of the important technologies required for the CMP process that is performed in planarization after formation of the insulating film or formation process for the metal interconnection, there is polishing end point detection. Because excessive polishing or insufficient polishing with respect to target polishing end point is directly linked to product defects, it is necessary to control a polishing amount strictly. From such circumstances, the end point detection monitor (EPM: End Point Monitor) which can monitor a change of film thickness with high accuracy during polishing has become an indispensable technology for the productivity improvement of CMP and the improvement of yield ratio of semiconductor products.
A sensor for the end point detection monitor comprises an eddy current sensor or an optical sensor, and is embedded in the polishing table to monitor a surface, being polished, of the substrate during polishing. Further, various sensors for monitoring the condition of the surface, being polished, of the substrate during polishing are embedded in the polishing table, besides the sensor for the end point detection monitor. Therefore, it is necessary to supply electric power from the outside of the polishing table to measuring instruments including various sensors provided in the polishing table. Further, it is necessary to send and receive input and output signals and to perform communication between the measuring instruments in the polishing table and equipments outside the polishing table. Thus, the measuring instruments in the polishing table are connected respectively to external power wires, signal wires, communication wires, and the like through a contact-type rotary connector (slip ring or rotary connector) having physical contact points. In order to allow these power wires, signal wires, communication wires and the like to be a waterproof structure, a waterproof structural object which encloses the contact-type rotary connector in its entirety is required to be provided.
Further, in the CMP process, because the substrate such as a semiconductor wafer is pressed against the polishing pad under a predetermined polishing pressure and is brought in sliding contact with the polishing pad to polish a surface of the substrate, a temperature in the contact surface between the substrate and the polishing pad, i.e., a polishing temperature increases. Since the polishing pad comprises a resin material such as foamed polyurethane, the polishing temperature changes rigidity of the polishing pad to exert an effect on planarization characteristics of the substrate. Further, since the chemical mechanical polishing (CMP) is a method for polishing the substrate by utilizing a chemical reaction between the polishing liquid (polishing slurry) and the surface, being polished, of the substrate, the polishing temperature has an effect on the chemical characteristics of the polishing slurry.
Therefore, a temperature sensor is provided in the polishing head for holding the substrate, and the temperature of the substrate or the temperature of the membrane for holding the substrate is measured during polishing. Further, various sensors for monitoring the state of the substrate or the polishing condition of the substrate during polishing are provided in the polishing head, besides the temperature sensor. Thus, measuring instruments including various sensors provided in the polishing head are connected respectively to external power wires, signal wires, communication wires, and the like through a contact-type rotary connector (slip ring or rotary connector) in the same manner as the polishing table.
However, the contact transmission structure having physical contact points such as a contact-type rotary connector has the following problems.
(1) It is necessary to replace parts of the contact transmission structure periodically due to wear or the like of the contact points.
(2) In the contact transmission structure having physical contact points, all the connectors are required to be replaced at the time of failure replacement.
(3) In the contact transmission structure having physical contact points, electric surge, noise or the like is generated from the contact points to cause an adverse effect on the power supply, signals, and communication circuits.
(4) In the contact transmission structure having physical contact points, the positional shift between the connector and the rotating shaft of the rotating body occurs to generate eccentricity of the connector.
(5) In the contact transmission structure having physical contact points, there are physical contact points to which electric voltage is applied, and thus waterproof protection becomes complex, resulting in a large-scale structure.